276 J. H. ASHWORTH. 



of a bluntj conical, anterior piece fixed to the spherical 

 nucleus. The length of the head is 7 fx, the nuclear portion 

 being 4 /n in diameter. The tail is a slender filament about 

 27 fi long. 



Tiie spermatozoa closely resemble those of Alcyonium in 

 their structure and development (Hickson, 1895). The endo- 

 derm covering the sperm sac appears to undergo certain 

 changes as the sperm sac grows, and in thin sections from two 

 to five nuclei may be counted in many of the endoderm cells. 

 One of these nuclei is sometimes larger tiian the others. In 

 the left upper cell of fig. 35 the large nucleus near the centre 

 occupies the position of the original nucleus of the cell. The 

 other four nuclei have probably been produced from it by 

 division, but there has been no corresponding division of the 

 protoplasm. The cell with four nuclei which was figured by 

 Hickson (1895, pi. 39, fig. 45, f.) from the teased prepara- 

 tions of the sperm sacs of Alcyonium, was probably one of 

 the cells of the endodermic follicle. 



At first it appeared that the sperm sacs were situated on 

 ventral and lateral mesenteries only, although, as pointed out 

 above (see p. 263), the cells in the mesogloea, from which the 

 genital cells are derived, are found in the dorsal mesenteries 

 as well. After examining a large number of sections, I have 

 found only two clear cases of sperm sacs occurring on the 

 dorsal mesenteries. In each case the sperm sac is situated 

 on the side of the mesentery a little distance from the free 

 edge, so that, although the sac is of considerable size ('15 mm. 

 in diameter), it does not push the dorsal mesenterial filament 

 out of position, and, judging from the sections, would not 

 impede its action. 



Empty sperm sacs the walls of which are collapsing may be 

 seen in several sections. The spermatozoa are discharged into 

 the coelenteron by bursting of the follicle of the sperm sac, and 

 arc then swept out to the exterior through the stomodseum. 

 In sections of two polyps in which spermatozoa were escaping, 

 the spermatozoa are found along the dorsal side of the stomo- 

 dseum, being doubtless driven out by the upward or outward 



